With the diminishing supply of crude mineral oil, use of renewable energy sources is becoming increasingly important for the production of liquid fuels. These fuels from renewable energy sources are often referred to as biofuels.
Biofuels derived from non-edible renewable energy sources, such as cellulosic materials, are preferred as these do not compete with food production. These biofuels are also referred to as second generation, renewable or advanced, biofuels. Most of these non-edible renewable energy sources, however, are solid materials that are cumbersome to convert into liquid fuels.
For example, the process described in WO 2010/062611 for converting solid biomass to hydrocarbons requires three catalytic conversion steps. First the solid biomass is contacted with a catalyst in a first riser operated at a temperature in the range of from about 50 to about 200° C. to produce a first biomass-catalyst mixture and a first product comprising hydrocarbons (referred to as pretreatment). Hereafter the first biomass-catalyst mixture is charged to a second riser operated at a temperature in the range of from about 200° to about 400° C. to thereby produce a second biomass-catalyst mixture and a second product comprising hydrocarbons (referred to as deoxygenating and cracking); and finally the second biomass-catalyst mixture is charged to a third riser operated at a temperature greater than about 450° C. to thereby produce a spent catalyst and a third product comprising hydrocarbons. The last step is referred to as conversion to produce the fuel or specialty chemical product. WO 2010/062611 mentions the possibility of preparing the biomass for co-processing in conventional petroleum refinery units. The process of WO 2010/062611, however, is cumbersome in that three steps are needed, each step requiring its own specific catalyst.
WO2010/135734 describes a method for co-processing a biomass feedstock and a refinery feedstock in a refinery unit comprising catalytically cracking the biomass feedstock and the refinery feedstock in a refinery unit comprising a fluidized reactor, wherein hydrogen is transferred from the refinery feedstock to the carbon and oxygen of the biomass feedstock. In one of the embodiments of WO2010/135734 the biomass feedstock comprises a plurality of solid biomass particles having an average size between 50 and 1000 microns. In passing, it is further mentioned that solid biomass particles can be pre-processed to increase brittleness, susceptibility to catalytic conversion (e.g. by roasting, toasting, and/or torrefication) and/or susceptibility to mixing with a petrochemical feedstock.